Why does Jesus permit divorce? Jesus gave the key for the permission of divorce by Moses as being caused by "the hardness of your hearts." Jesus told the Pharisees that Moses gave the law of divorce "because of the hardness of your hearts " [Strong's G4641, Mark 10:5; Matthew 19:8]. The ISBE defines the Greek sklerokardia as "dryness," "stiffness of heart." At the beginning in Eden there had not been any "hardness of hearts". "Hardness of hearts" is the arena for sins. Jesus explained at another time, "For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies: These are [the things] which defile a man: but to eat with unwashen hands defileth not a man" (Matthew 15:19-20).

      Jesus had already been angry with the Pharisees earlier in His ministry (Mark 3:5) when on the Sabbath He was healing the man with the withered hand. He was grieved with them because of the "hardness of their hearts."

      The hardening of men's hearts is attributed both to God and to man himself in both the Old and New Testament. The Egyptians' hearts, for example, were hardened by God (Exodus 4:21; 7:13; 7:22; 8:19; 9:12; 10:20; 10:27; 14:17; etc.). Hardening of the heart is also attributed to the Egyptians themselves (Exodus 8:15; 8:32; 9:7; 9:34). In the Hebrew there are two different words used for hardening; one refers to God and the other to the man; but the result is the same. God commands; man bucks up and says "no." Both have caused the act. If man doesn't want to obey God, then whatever God requires will produce the obstinate refusal to comply.

      Paul's audience was not always receptive to the teaching. "But when divers were hardened (skleruno), and believed not, but spake evil of that way before the multitude, he departed from them, and separated the disciples, disputing daily in the school of one Tyrannus" (Acts 19:9). Paul preached the gospel. Many refused to believe and began attacking the messenger of truth. God had given the opportunity to be saved or to rebel. Many rebelled. As Paul says (Romans 9:18),"Whom He will He hardeneth" (skleruno).
      "Hardness of hearts" are stubborn hearts because of unbelief; this is the same as disobedience (Hebrews 3:18,19 ASV, ESV2011, Mickelson, Strong); hence, sin. "The heart is hardened by the deceitfulness of sin" (verse 13). The writer of Hebrews two times quotes a reference to Israel's sins that brought about their deaths in the wilderness. "To day if ye will hear his voice, harden not your hearts [G4641], as in the provocation" (Hebrews 3:15 and 4:7). "But with whom was he grieved forty years? [was it] not with them that had sinned, whose carcases fell in the wilderness? And to whom sware he that they should not enter into his rest, but to them that believed not? So we see that they could not enter in because of unbelief [G570]" (Hebrews 3:17-19).

      The descendants of those that were given a home in the promised land responded to God with their unbelief. Eventually then, God had to punish the nation by removing them from the land. Why? As God explained to the prophet, "But the house of Israel will not be willing to hearken to thee; for they will not hearken to me: for all the house of Israel are stubborn and hard-hearted" (Ezekiel 3:7).

      Jesus condemned even His apostles for their hardness of hearts for their initial unbelief in His resurrection. "Afterward he appeared unto the eleven as they sat at meat, and upbraided them with their unbelief [G570 ?p?st?a apistia] and hardness of heart [G4641] because they believed not them which had seen him after he was risen" (Mark 16:14). See also Mark 6:52.

      Why did God say that Judah of old had hardness of hearts (sklerokardiav)? It was because their doings were evil. The prophet warned Judah in Jeremiah 4:4, "Circumcise [peritemesthe] yourselves to the LORD, and take away [circumcise peritemesthe] the foreskins of your heart [G4641 sklerokardia] ye men of Judah and inhabitants of Jerusalem: lest my fury come forth like fire, and burn that none can quench [it], because of the evil of your doings."

      God warned the prophet Ezekiel that the house of Israel would not listen to him because they would not hearken to God. Why? Because "all the house of Israel [are] impudent and hardhearted" (Ezekiel 3:7b).

      Application to Matthew 19:8.

      Sometimes we interpret the Bible through what I call "colored glasses". We have a preconceived idea about something and when we are confronted with new information, we let our bias color our understanding of the new information. We have been told that Christians are to forgive any and every harm that comes our way even to our detriment. Hence, with such a bias, one thinks that Jesus was saying Israel didn't know how to forgive their spouses [but we do?] and had to be given permission to divorce. Since Christians are to forgive, then they are not allowed under the New Testament to divorce the offending partner. But of course that is not Jesus talking; it's the theologian.

      Who has the hardness of heart? All one has to do is put the shoe on the other person's feet. That is, the party that sinned is the one with the hardness of heart. The Law of divorce given through Moses was not given because an innocent couldn't forgive. It was given because the offending party had a hardness of heart and stubbornly violated their responsibility to the marriage. If anything, it was given for mercy to the innocent party. And that is why Jesus gives His law of divorce (called the "exception").